With the recent popularization of copiers, printers and the like, environmental regulations on human health in office environments have become established mainly in Europe. Further, in high-speed printing, the amount of the toner to be consumed per unit time for development of electrostatic images increases, and therefore more volatile organic compounds and dust would be thereby diffused.
In addition, the arena of electrophotography is expanding not only in the field of letter printing for the past office use or the like but also in the field of graphic use for photographic printing and others, and the amount per sheet of the toner to be used for development of electrostatic images is increasing exponentially.
With such changes in needs, calls to providing a toner for development of electrostatic images that would hardly diffuse volatile organic compounds and dust even in a case where the amount of the toner to be consumed per unit time for development of electrostatic images is large in high-speed mass-scale printing are being strengthened year by year.
Recently, image forming devices certified by the most strict environmental standard, “The Blue Angel” have become increasing, and in electrophotographic fixation systems, the substances that are generated during high-temperature fixation and diffused out of the systems, concretely, dust by sublimation substances and volatile organic compounds are desired to be not more the controlled level regulated in ECMA-328/RAL_UZ122.
Also in Japan, as the certification standards for the ecology mark for copiers, duplicators and the like, the regulation values of RAL_UZ122 are employed as they are at the time of re-revision in 2008, and the related devices are required to satisfy the standards.
The majority of causative substances for the dust that is a substance to be generated and diffused out of systems during high-temperature fixation are the wax components contained in toner. In a high-temperature fixer where papers with a toner transferred thereon are led to pass therethrough for fixation thereon, the wax in the toner not only melts to exhibit a release effect but also partly sublimes to cause dust emission. Dust is a result of the physical sublimation phenomenon of the wax components, and therefore it is desired to provide a method of inhibiting sublimation itself of wax.
In general, wax having good releasability tends to provide a large amount of dust. This is because, the wax that may readily bleed out of a binder resin during fixation is non-polar and is therefore non-compatible with a binder resin, or has a low molecular weight and therefore has a low melt viscosity. The wax of the type a weak intermolecular force between the wax molecules or between the wax molecule and the binder resin, and therefore may often sublime during fixation to form dust.
On the contrary, those having polarity such as ester wax and the like, or high-molecular-weight waxes, and further those having a high content of unnormalized forms such as iso-form, cyclic form and the like of hydrocarbon waxes hardly bleed out during fixation owing to the above-mentioned intermolecular force and to entanglement of wax molecular chains, and in general, therefore, they tend to be relatively poor in releasability but they hardly sublime and the dust emission amount from them is small. In other words, it may be said that releasability performance and environmental performance are warring concepts.
Under the trend as above, for example, PTL 1 proposes a toner for development of electrostatic images which satisfies both low-temperature fixation capability and blocking resistance while preventing dust emission during fixation.